1. I need to have only numbers for captcha validation images as my client is complaining that typing to get validated is pain (frustrated with auto-correction) on smartphone. I went into "wavt_captchasecurityimages.php", then I figured and I god rid of all the alphabets;

$useChars = '123456789';

It doesn't show alphabets anymore, but a square text appears with numbers.(Image attached.)

How can I get rid of this?

2. Is it possible to implement Google's reCaptcha (one that came in 2014 that you only need to click to "I'm not robot") to existing form build with Form builder?